The technique of holography has provided a new method for study of environmental situations which heretofore could not be approached. In particular, the possibility of studying the dynamics of particles and fibers in the atmosphere or in a duct by direct observation without the intrusion of measuring devices, now exists. The combination of pulsed lasers with the holographic method will permit a "stopping" or "freezing" of the motion of possible dust pollutants in space, such that their flow patterns can be observed both qualitatively and quantitatively. We propose to use this methodology to attain the following objectives: 1) Determine the speed and mode of fall of fiberous and platy materials (e.g., asbestos, glass fibers, talc, etc.) as they move through space. (does an asbestos fiber 2 microns in diameter and 20 micron long move perpendicular to its long axis, parallel to it, or does it tumble?) Establish how the rate and type of movement varies with size, shape, and concentration of particles per unit volume; and compare this with the values obtained using mathematical formulas and experimental data developed previously by others for the movement of particulate matter. 2) Determine the action of fiberous and platy materials as they move or are drawn to the face of filters of various types at various speeds. What can be done by varying the rate of air flow through the filter to change this mode of motion for a more efficient collection? 3) Determine the effect of a surface on the same types of dusts as they move toward the face of a filter.